Increment sensing with three beam mark detection

Abstract

The present invention relates to the digital control of a machine or equipment, particularly but not exclusively a matrix printer under utilization of an increment step sensor monitor or pick up operating on the basis of optic electronic principles and including at least one source of radiation and at least two pickup transducers disposed in the ray path from the source of illumination and further including a marker track composed of alternating transparent or translucent and opaque increments being unilinearly moveable, either on a curved or on a straight path.

We claim: 
     
       1. In a device for digital control of a machine or movable equipment part under utilization of a drive asociated with an optical electronic increment sensor, the improvement comprising: a plurality of parallel track defining means with each track being defined by alternately translucent or transparent and opaque incremental marking sections;   means defining a corresponding plurality of groups of three separate beams each, the beam of each group traversing one of each said of the increment track means, two beams of each group being close to opposite outer borders of the respective track marking and a third one of the group of beams traverses the respective center of that track;   said beams of any of said groups being arranged so that projections of the beams of the respective group into a plane of the respective track result in scanning dots being arranged along a line having an oblique angle in relation to the direction of extension of the respective track marking sections;   three beam combining means, respectively (i) combining the beams of all groups having traversed one border of each marking of the plurality of tracks (ii) combining the beams of all groups having traversed another border of each said marking of the plurality of tracks; and (iii) combining all beams of the groups having traversed the respective track centers; and   pickup means for separately detecting illumination from the three beams as modulated by said marker tracks and as combined as per (i), (ii), and (iii) and providing separate electrical signals respectively representing passage of one border of all tracks, of another border of all tracks, and of the center of all tracks.   
     
     
       2. The improvement as in claim 1, wherein said pickup means include three separate photoelectric transducers. 
     
     
       3. The improvement as in claim 1, the pickup means being a triple photodiode. 
     
     
       4. The improvement as in claim 1, the beam defining means being a triple light emitting diode. 
     
     
       5. The improvement as in claim 1, wherein said angle is chosen so that signals as derived by the pickup means from the track borders in each instance are in phase opposition, a third signal being respectively plus and minus 90 degrees phase shifted to the former two signals. 
     
     
       6. The improvement as in claim 2, there being three tracks and means defining three separate scanning beams for each track, arranged so that each track is traversed along its border by outer beams and by a central beam; and means for combining corresponding beams having traversed one border each, in one of the two transducers, other outer beams having traversed another border each of the tracks in a second one of the three transducers; and other beams having traversed central track portions in a third one of the three transducers. 
     
     
       7. The improvement as in claim 5, including circuit means for separately combining the signals having phase opposition with the third signal as reference signal. 
     
     
       8. The improvement as in claim 1, wherein light conductors run separate beams towards the tracks, and further light conductors run light from the tracks to the pick up means, the light conductors being oriented so that the tracks are traversed by beams at right angles. 
     
     
       9. The improvement as in claim 6, wherein light conductors run separate beams towards the tracks, and further light conductors run light from the tracks to the pick up means, the light conductors being oriented so that the tracks are traversed by beams at right angles. 
     
     
       10. The improvement as in claim 1, wherein separate light conductors run from the tracks to the transducers in crossover relation. 
     
     
       11. The improvement as in claim 6, wherein separate light conductors run from the tracks to the transducers in crossover relation.